Masson Fontana staining demonstrates melanin and argentaffin granules. Which tissue is used to demonstrate melanin?

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Masson-Fontana staining highlights melanin because melanin acts as a reducing agent and reduces silver ions to metallic silver, giving a black deposit in pigment-containing cells. This makes it ideal for identifying melanin in tissues with melanocytes, such as pigmented nevi. In a nevus, the melanocytes produce melanin, so the stain will darken where those cells lie. Other tissues like the liver or spleen lack significant melanin, so they won’t show this dark pigment. The small intestine can show argentaffin granules in enteroendocrine cells, but that reflects a different substance, not melanin. Thus, nevi are the tissue that best demonstrates melanin with this stain.